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Scientists from Nanyang Technological University have discovered the likely source of a late 18th century tsunami which happened in southwest Taiwan. This was the largest and most fatal tsunami ever reported in the South China Sea.

Asst Prof Adam Switzer, from NTU’s Earth Observatory of Singapore (EOS) and the Asian School of the Environment (ASE) who led the multidisciplinary research team, said this finding raises serious questions about the safety of the southwest coast of Taiwan.

“A similar event today like that in the 18th century, would endanger millions of lives in the coastal cities like Kaohsiung and Tainan and damage infrastructure located at the south of Taiwan,” warned Asst Prof Switzer, a coastal hazards expert.

The findings of this study were published earlier this month in Geophysical Research Letters, a peer-reviewed scientific journal published by the American Geophysical Union.

The study was part of a National Research Foundation (NRF) Fellowship awarded Asst Prof Switzer to investigate coastal hazards in Asia. It involved a team of five from NTU, in partnership with Assoc Prof Robert Weiss from Virginia Polytechnic Institute and State University (Virginia Tech) in the USA.

The investigation into this 18th century tsunami, which had a reported death toll of over 40,000 people, was started by Asst Prof Switzer and Dr Li Lin Lin, an EOS research fellow.

Dr Li had compared three different historical accounts of an unexplained late 18th century event from mainland China, other parts of Taiwan, and the northern Philippines. The comparisons convinced the team it was a large tsunami that hit the southwest coast of Taiwan but had little impact elsewhere, which was quite unusual.

The team then tried to simulate how the tsunami was generated via software to no avail, even though all identified tsunami sources, such as volcanic explosions and earthquakes were accounted for.

“No matter what parameters we put into the earthquake or tsunami model, we could not re-create the tsunami described in the historical records,” explained Asst Prof Switzer.

“So we concluded that that an earthquake alone was not capable of generating the tsunami and something else must have happened. Sure enough, a huge underwater landslide (known as a submarine landslide) gave the extra push we needed for the simulation to succeed.”

Analysis showed that the 18th century tsunami was likely generated when an earthquake triggered a large underwater landslide on the upper portion of the continental slope offshore from southwestern Taiwan. This happened sometime between 1781 and 1782.

Prof Paul Tapponnier, Group Leader of Tectonics at EOS and the co-author of the study, said their work confirms that a historically large and fatal late 18th century tsunami event had occurred and would have flooded Kaohsiung in southern Taiwan.

“Based on history, we know that large earthquakes and tsunamis which have happened before will likely happen again in the future, although forecasting them will be difficult due to the sparse historical record of the region,” added Prof Tapponier, a world-renowned tectonics expert who accurately forecasted the Nepal earthquake before it happened in April this year.

Asst Prof Switzer added that the surrounding infrastructure in southern Taiwan, which includes the Maanshan Nuclear Power Plant, remains exposed to similar potential tsunamis generated by submarine landslides and earthquakes from the same area, which implies a clear need for adaptive measures to be taken.

In addition to tsunamis, underwater landslides in the same area will also endanger underwater telecommunication cable lines, some of which are densely deployed south of Taiwan and connect South-east Asia with the rest of the world.

As demonstrated by the 2006 SE Asian communication failure, which was one of the largest disruptions, damage to the underwater telecommunication cables will severely affect and disrupt financial markets, commerce and general communications (banking, airline bookings and email) for weeks.

“There is a need to educate people and travellers on what to do when they are in coastal areas at risk of a tsunami and an earthquake hits. Upon feeling an earthquake, the best thing to do is to move quickly to higher ground, such as into a building three storeys or higher, and away from beaches,” Prof Switzer said.

A research-intensive public university, Nanyang Technological University, Singapore (NTU Singapore) has 33,500 undergraduate and postgraduate students in the colleges of Engineering, Business, Science, Humanities, Arts, & Social Sciences, and its Interdisciplinary Graduate School. It has a new medical school, the Lee Kong Chian School of Medicine, set up jointly with Imperial College London.

NTU is also home to world-class autonomous institutes – the National Institute of Education, S Rajaratnam School of International Studies, Earth Observatory of Singapore, and Singapore Centre on Environmental Life Sciences Engineering – and various leading research centres such as the Nanyang Environment & Water Research Institute (NEWRI), Energy Research Institute @ NTU (ERI@N) and the Institute on Asian Consumer Insight (ACI).

A fast-growing university with an international outlook, NTU is putting its global stamp on Five Peaks of Excellence: Sustainable Earth, Future Healthcare, New Media, New Silk Road, and Innovation Asia.

The University’s main campus has been named one of the Top 15 Most Beautiful in the World. NTU also has a campus in Novena, Singapore’s medical district.